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Reincarnated in Mushoku Tensei: Realistically Overpowered (fanfic)

A reader reincarnates in the world of Mushoku Tensei as Seraphim Greyrat, the first son of Paul and Zenith born instead of Rudeus. Using his meta knowledge to the fullest, he aims to become the strongest existence of that world, using both sword and magic. ... Warning: A SLOW PACE FANF-FIC WITH A LARGE FOCUS ON MAGIC STUDY AND WITH A HIGH LEVEL OF DETAIL. STARTS OFF SIMILAR TO CANON. Seraphim studies the magic system of the world and Battle Aura techniques in depth to understand them fully and gain the best possible advantages. He becomes overpowered without external cheats, a result of his hard work and brains. Note: How this fanfiction is different from others in that many Mushoku Tensei fanfics seem to often get the magic system of the world wrong. The abilities that the Protagonists develop often go against the magic system of the world, are illogical and ridiculous, and something like this in my opinion completely breaks immersion. For example, ridiculous new magic spells and OP sword moves that get invented by an infant MC despite the fact that they are completely devoid of logic and are just impossible without cheats. Here, my Protagonist faces various obstacles and problems during training, that he should, while also gaining insights and does what is realistically possible to take his training and fighting methods to another level. He also achieves things that seem nearly impossible or fantastical, but with good logic and reason behind them. -It is a harem story, but I aim for meaningful romance and deep relationships. It is a harem story. However, harem is not the major focus of the story at all. It only means that the MC will have more than one partner EVENTUALLY. -Because the Protagonist accomplishes A LOT during his early years, there might be no real romance or even harem content anyway for something like 100 chapters. There will be no child sex here as well. There might be some romancing and teasing, but just that, nothing sexual. How this story is different from the original is that it is not about an MC searching for a cure for his ED, being passive and pathetic pervert all throughout the story while screwing around and doing nothing most of the time, but is a man on a mission. Seraphim starts from a similar point as Rudeus, but his actions cause a slowly spreading butterfly effect as he's focused on the most optimal path and BENEFITS. In contrast to Rudeus's perversion, the MC can sometimes instead be amoral and do evil pragmatic things for the sake of his ambitions and loved ones, so people with fragile hearts be warned. He is not as disgusting, but it doesn't mean he's a goody-two-shoe white knight. ... SUMMARY: -MC is born instead of Rudeus with just his meta knowledge and high talent. Taking more after Zenith, he has blonde hair and blue eyes. He trains his mana from an extremely young age, masters Battle Aura and chantless healing magic | A genius of magic and the sword, a determined true main character pursuing supremacy and eternal life. -The story will have a deep dive into the magic system and how the MC interprets it (how I interpret what we know using logic). It might be boring for some people, but it can be very interesting for others (would be for me). -The story starts with the same layout, and has slowly spread out changes as the MC is focused on BENEFITS. -The world is the same as in the original, the only AU change is the MC's body, looks and name.

Jaed21 · Anime & Comics
Not enough ratings
46 Chs

Chapter 21. The Boreas family

It was evening when the carriage arrived in the City of Roa, after around six hours of travel.

The first thing that caught the eye were the citadel's walls. Sturdy walls, seven to eight meters tall, wrapped around the city.

It wasn't just the lord's manor that was fortified, but the entire city was well protected. To surround the entire city with such a wall, something like this would have never been done back on Earth. 

'Should be the result of Earth Magic,' I thought.

Horse-drawn carriages came and went through the gigantic gate.

As our coach passed through it, I saw lines of merchant stalls lined up along the street.

The first building behind the gate was a large stable and something that looked like an inn.

A crowd of people bustled to and fro: merchants, townspeople and even armor-clad warriors. It was truly a view from a fantasy novel.

As the carriage continued in silence, we eventually approached the lord's manor which more resembled a castle.

I didn't talk with Ghislaine much and she also did not tell me much about the Mistress that I'm supposed to train with either, but I felt that the atmosphere was rather comfortable.

Each of us acknowledged the other's strength and thought well of the other, I suppose.

Soon enough the carriage came to a stop.

After we entered the manor, a butler led us to what looked to be a reception room. We were pointed toward two sofas lined up together.

"Please take a seat."

As I sat on the sofa, Ghislaine silently drew away and stood watch in the center of the room with a serious business-like face.

'Pretty cool.'

"The Young Master should be here shortly. Please wait until he does."

The butler poured what seemed to be tea into an expensive-looking cup. Then he retreated and stood by the entrance of the room.

I took a glance at the cup first.

Glassware and detailed ceramics are rather expensive in this world.

I could later simulate and copy this cup with Earth magic. After being painted, it could be sold for a good amount of money. Perhaps if I made my products especially durable, they might become a popular brand?

These could be produced en masse, rather than figurines that require immense level of detail.

Having these kinds of thoughts at the back of my mind, I took a sip of the steaming drink.

"Ghislaine!!!"

At that moment a loud shout was heard.

Then the doors burst open.

I looked in that direction.

However, contrary to my expectations, the person shouting and bursting in was not the lord of the Boreas, but a young red-haired girl.

An arrogant and fierce expression, being two years older than me. Her eyes were sharp and narrow, her hair wavy and crimson red.

She placed her hands on her hips, looked at Ghislaine and called out joyfully, "Ghislaine, you're back!!!"

"Yeah. I'm back, Eris Ojou-sama." Ghislaine nodded slightly.

The two were looking at each other and I was completely ignored.

I put down the cup of tea and prepared to get up.

*Eris* looked at Ghislaine for a while, then turned toward the center of the room, toward me.

Seeing me, she spread out her legs wide, puffed out her chest and crossed her arms as she glared down at me and snorted. "Hm! That's him?!"

I stood up from my sofa and did a noble's greeting. "My name is Seraphim Greyrat. Are you the Young Miss I'm supposed to train with?"

Eris narrowed her eyes and raised her voice. "What is this?! You're younger than me!"

"It seems to be this way," I replied calmly.

"I'll crush you to bits!!!"

My gentle smile did not waver. "I heard you're very talented with the sword. I look forward to training with you."

"Hm! I'll beat you to a pulp!"

Eris glared at me, but I felt she seemed rather happy after I complimented her.

"Where is he?!"

Another loud shout was heard from the outside.

"In here?!"

A buff muscular man entered the room. He looked around 50, but despite a peppering of white in his hair, he looked rather lively and energetic.

"Grandfather!"

As Eris called out to him, the middle-aged man glanced at her, then his sharp and fierce gaze swept through the room and settled on me.

I slightly gulped.

But it's alright. I'm already well prepared for this. Beforehand I learned the basics of Asuran noble etiquette from Lilia.

I placed a hand on my heart and bowed slightly in a trained motion. "My name is Seraphim Greyrat, son of Paul Greyrat. It's nice to meet you."

"Hm! You're Paul's kid? You don't look like it!" The middle-aged 'grandfather' replied in a very loud voice.

"I took more after my mother."

"So that's it! I see Paul at least taught you some manners! Good. I will permit you to stay here!"

After saying that, the master of the house turned and strode out of the room, his chest puffed out and shoulders broad.

As if imitating him, Eris let out a snort and then directly left the room with wide and strong steps as well.

The two entered like a storm and left like a storm.

"That man is the liege lord of the Fitoa Region, Sauros Boreas Greyrat. He is also Master Paul's uncle. Meanwhile that young girl is his granddaughter, Eris Boreas Greyrat."

"I see."

Well, I already knew that.

"What's going on, Thomas? You left the door wide open." Someone appeared in the doorway: a thin, lightweight man with sleek brown hair. "It seems like Father and Eris are in a good mood. Did something happen?"

The butler Thomas said, "This is the Young Master. Pardon me. Just a moment ago the Master and the Young Miss met with Lord Seraphim. It seems they got along well."

"Ah-ha. But if they got along well, then perhaps I have invited the wrong person?" He took a seat on the sofa across from me with a slight smile.

'Time to introduce myself.'

Just like a moment ago, I did a noble's greeting by placing a hand on my heart and slightly bowing. "It's nice to meet you. I'm Seraphim Greyrat, son of Paul Greyrat."

"Ah, yes, and I am Philip Boreas Greyrat. Your manners are quite good for someone so young, and especially Paul's son. I suppose that's why Father was pleased, isn't it?"

"I think so."

"I can imagine. Now please, sit down." He flounced back upon the sofa with a thud.

Following his example, I also sat down.

Philip said, "So what's your first impression of my daughter?"

"Of Eris?... It seems she's very energetic." I smiled.

"Is that so?..." Philip smiled. "Well, I heard you got along well. How did this happen?"

"I was only polite. She was determined to crush me to bits, though."

"Haha. I see." He chuckled, then put his hand on his chin and gazed at the table as if lost in thought. He then asked, "Say, do you like girls?"

"Eh?... I guess. But not as much as Father." I smiled wryly.

"Is that so? Then it's fine!" Philip smiled. "Paul is the type of man who would go to any lengths if it was for a cute girl, so I figured you might have been the same."

My wry smile intensified.

I'm supposed to be 5. Just what were you suspecting?

"Anyway. Like I wrote in the letter to Paul, my girl is a little spoiled. She looks up to her grandfather and is a bit violent. I hope you'll be tolerant."

"Yes."

"Yes, Paul has praised you a lot… But among other things, it seems that you're a very talented young magician?" Philip looked me in the eyes with some kind of analytical expression.

So it's that. I wonder just how much Paul had told him.

I hesitated for a moment, then nodded, "Yes, it's true. It seems I'm quite talented at magic."

"Oh my, how humble. You seem very bright for your age as well. But it's still very shocking for a 5 year old to have achievements like yours, fantastical even. Paul likes to brag and tell jokes, but I don't think he would go that far. Ghislaine, what do you think?"

Okay, so he should already know I'm Saint ranked. I knid of expected that.

Still, I'm glad he didn't outwardly babble about it.

As Philip looked at her, Ghislaine replied, "I've seen Seraphim's magic. I don't think it's false. He's very talented."

"Is that so?"

Ghislaine nodded. "If I let down my guard, he might even defeat me."

"Oh. Interesting you would say that…" Philip muttered in surprise.

"Only if I have enough time to send out my magic," I added to downplay myself and then sent Ghislaine a meaningful look.

Before this I told her to not talk about my real combat strength.

Ghislaine was expressionless. She probably thought that it was fine to tell Philip.

But I personally did not like the look of that butler Thomas.

Philip glanced at me again, but this time his attitude seemed to have slightly changed. He placed a hand on his chin and after a few seconds said, "Anyway, I heard from Paul that at your age you're also skilled at reading, writing and arithmetics. Is that true?"

"Yes. My parents and Master taught me from a young age."

"Ha-ha! Paul being so focused on education, it's really the first! Haha," Philip burst into laughter.

"..."

"Sorry… In truth, the reason I invited you to Roa is not only because Paul asked me to find you a sparring partner, but because I hoped that you'd be somehow able to influence my daughter to make her begin studying. If the two interacted, just what would happen, I wondered... Though, to be honest, I don't expect much."

"..."

"At the very least, both of you could improve your swordsmanship by training together, so there is no loss, right?" Philip looked at me. "I only have to warn you to not be too violent with my daughter and not hurt her with magic. If you do, I'll have to send you back."

"I understand."

"...Well, that would be it for today. We'll see how it goes." Philip stood up. "Your first swordsmanship lesson will happen tomorrow, right, Ghislaine?"

"Yes. I'll still do Eris's training before nighttime, but Seraphim can take a rest. I heard he already trained."

"Alright. Seraphim, then for now you can settle in your room. I'm sure you're tired after the journey."

"Yes."

"Welcome to Roa."

The meeting ended like this.

I was able to live in the lord's manor and would receive lessons from Ghislaine the Sword King for free while I'm here for a month, so it was certainly a good deal for me.

The mansions' workers guided me to the place where I was supposed to live from now on.

The room was exquisitely furnished. It had a large bed and other heavily decorated furniture, beautiful curtains, and a brand-new bookcase.

This had to be a guest room, rather than a servant's room, given to me because I was a Greyrat and technically a guest.

Most of the maids in that place were beastfolks, as expected.

The butlers brought in my baggage for me and the maids brought me a warm dinner.

From what I knew, among Asuran nobility it's a rule that servants are not allowed to eat together with the masters. 

Because Paul detests noble formalities, our family back in Buena village was an exception and he always invited Lilia and Roxy to eat with us, which surprised Roxy, but Rudeus probably didn't dine together with the Boreas because of this rule - he was invited in as a servant, a home tutor.

I felt like I was a guest instead.

But I suppose my status and age wasn't high enough to partake in a welcoming feast with everyone. There were probably politics involved as well.

I didn't mind.

That day I had already done my strength training workout back at the village and used up my magic during travel, so I was fine on that front.

I was tired after the journey and after taking care of basic hygiene, eventually went to sleep.

Next day in the morning was my first lesson with Eris under Ghislaine.

As I entered the training square, the young miss was already there.

She stood with her legs wide and arms crossed in front of her chest, her chin pointed up.

"You're late!!!" She called out, glaring at me.

I frowned.

I was not late.

I mean, Ghislaine just brought me here and Ghislaine herself got here just now!

I think it's her who was simply early. But I decided to not speak up.

I said nothing. No arguing.

Eris was 2 years younger than in the novel. I see. If anything, she would only be more barry and simple minded than normally.

"Eris, you got up early today," Ghilsaine said.

"Of course!"

Eris answered matter-of-factly as if it was obvious.

But I felt as if she had gotten up especially early today just to rub it into my face and to beat me up…

How this confrontation would go, I am not sure.

I believed in my hard work these years, but in the end Eris was 2 years older and I was not entirely certain of my grade of talent.

Either way, I would ideally crush her ego here and make her respect me a little, all while at the same time not being rude.

For this, I could always secretly cheat using Gravity Magic.

I felt I had good chances against a silly 7 year old brat.

"Seraphim, how much training with the sword did you do?" Ghislaine asked me.

"I trained since I was 3 years old."

"Eh? That's even longer than me!" Eris called out in surprise.

"No. He's 2 years younger than you, so he didn't train longer. Uh, he's now 5, so if he trained since he was 3, he trained for…" Ghislaine started counting her fingers, then said, "You trained for 2 years, right?"

"Yes."

"Woah, Ghislaine, you can do math too!" Eris praised, her eyes sparkling.

"No… Even I can do that much." Ghislaine was expressionless.

Yeah, it isn't really something worthy of praise…

Ghisaline said, "You both trained for 2 years, so I'll just still start with the basics."

We were made to pick up the wooden longswords.

After picking up the training sword, I immediately felt that it was not quite designed for a 5 year old to use. It was slightly too long and heavy.

It wasn't very heavy, but it was not exactly weightless either.

But that was only to my advantage.

I modified gravity around my body to make everything half as light.

The wooden sword in my hand then became as light as a dry tree-brunch. My entire body also became much lighter.

Since I always had another dedicated strength training unit in a day, sword-training for me was mostly about stamina and technique. There was no demerit in doing this and helping me to train at maximum proficiency for longer. 

That's just for this sparring session anyway. My goal today was to overpower Eris, so I had to converse my strength. I had to bring down her arrogance a notch today, otherwise she'll never begin to respect me.

We first began to do practice swings by imitating Ghislaine, and Ghislaine was correcting our forms.

The difference between Paul's and Ghislaine's teaching methods could be immediately felt. She was actually able to tell me how I can improve.

That being said, I think I have built up a decent foundation thanks to Paul.

Ghislaine didn't have many complaints, so I believe I was doing quite well.

Next to me, Eris also repeated the moves silently while from time to time sending me condescending looks of superiority.

Not long later it was time for me and Eris to have a 'light spar'. Ghislaine wanted to judge our levels during free sparring.

Holding longswords in both of our hands, Eris and I stood opposite each other.

My face was expressionless and focused, while Eris's expression was fierce - her nostrils flared and she glared at me like a bull preparing to charge at its target.

"I'll crush you to bits!" she declared.

I was silent.

"Begin."

Ghislaine signalles us to start, and like a wild beast let out of her cage, Eris charged at me with her sword.

I already expected this and took a defensive Water-God Style stance I mastered with Lilia.

With a clear opening on my chest, Eris went for it and executed an honest merciless diagonal cut.

Not a thrust. Typical of Sword God users.

It only made things easier.

It was a fierce strike that should have had most of her strength behind it, but it was too obvious.

My body light and fast, I smoothly deflected the strong sword strike, then counter-attacked with a swift wrist flick like attack.

My movement was very quick, minimal and not at full strength, but the result was profound.

"Aaah!" Eris cried out as she let go of her sword. She grasped her hand with her face contorted in pain. Holding her hand, she roared at me in anger: "You bastard! You hit my hand!!!"

"Let me heal you," I did not argue and simply said this clearly.

After letting go of my sword, I approached Eris with a neutral expression.

But the moment I entered her range, she pulled back her other hand and elbow, and shot out a punch straight at my face with a fierce expression and a shout.

I raised my left hand and caught it. I caught her fist.

It wasn't easy, but I did it!

Fortunately, I already predicted this. Eris's punch was quick and strong, but the telegraph was predictable.

But ouch, that hurt my palm!

Still, I maintained a nonchalant face on the outside and clearly spoke up, "I said, let me heal you!"

Holding her fist, I poured healing mana into her body while muttering, "Healing."

The mana quickly flowed along her arm, then through her torso and eventually reached her other hand to heal it.

I think I looked pretty cool doing all this.

After being done, I let go of her hand, keeping careful watch of any other attacks that might be flying my way.

But Eris only looked at me with an amazed and confused face. "The pain… is gone."

"I'm sorry I hurt you, but when using a sword, the goal is to strike the opponent's body, not their sword. You know this, right?" I said this while trying to sound as neutral as I could.

"... Of course!" It seemed she was about to rebuke me at first, but eventually answered in a tone of a bratty know-it-all. "Hmph! I'll beat you this time!!!"

Phew. I let out a breath of relief inwardly.

She's easy to predict!

"Seraphim, pick up your sword and go again," said Ghislaine, her eyebrows raised.

And so we went at it again.

But despite saying that she'll beat me this time, Eris did not beat me the second time either.

I narrowly deflected her obvious attack using Water God Style, then increased gravity on my next attack and knocked her sword out of her hand with a heavy blow.

As she went to pick up her sword while grinding her teeth, I felt a bit cocky and had an urge to slap her butt with the flat of my sword, but I held back.

The goal was to defeat her and bring down her arrogance without disrespecting her. This was the key!

Even if I beat her, if she felt insulted, it would only backfire and she would resent me more.

I knew that much from reading novels and watching anime.

I might fail in picking up a normal girl, but I felt I had higher chances in getting along with a violent tsundere in a fantasy world.

On the next attack, Eris's strike was too wild for me to predict, and my shoulder was struck. But Eris's fingers were also hit by my sword.

With a loud pained scream she let go of her own sword, and I followed up with a strike to her neck.

"Aarrgh!"

While Eris was groaning and starring daggers at me, I approached her to heal her. "I'll heal you."

She did not counter-attack this time and simply allowed me to grasp her wrist.

Sending mana into her wrist, I quickly healed her.

She looked down at me.

She, literally, looked down at me, since I was shorter.

"How did you do that again?! I demand you tell me!"

"I'm a bit of a magician."

"So it's magic!"

"Yes. Can't you use magic?"

"I never learned it!"

"If you learned magic, you could have healed yourself without me having to do it."

"No need! If I want to be healed, I can have someone do it!"

Yeah, I guess.

Still, I said, "Yes, but what if you're adventuring and you have no healer?"

Eris was at a loss for a while, but then made a comeback: "If I went adventuring, I'd just take a healer with me!"

Hearing this, I looked at Ghislaine and asked, "Ghislaine, were there times when you were wounded and didn't have a healer?"

A reminiscing look appeared on Ghislaine's face and she said, "Yes. Many times, actually. I was in pain for days before I could reach a city and find someone to heal me."

Eris's expression turned very complicated at that moment.

I told her, "That's why it's always good to learn some magic."

"Hmph! Are you looking down on me because I don't know magic?! Who do you think you are?!" She glared at me, shouting angrily.

"I don't look down on you. But I think someone clever like you would understand that it's useful to know magic."

"...Of course! I just didn't bother to learn it!!!"

After that, sparring continued.

From the beginning I was already prepared for what to expect from Eris, and was prepared to be patient.

I knew her potential, and that's why I could bear with her for the time being. For the greater good!

Not far away, Philip forced a wry smile while simultaneously shaking his head as he secretly watched this scene from the balcony.

He previously told Ghislaine to allow the two to interact and talk instead of purely focusing on training them, but he didn't expect Paul's son to be so smooth with his words and in bewitching young girls.

Paul's son was Paul's son. Scary.